1. Technical Field
The present application relates to a communication device provided with a pair of communication lines, an on-vehicle communication system including the communication device and an inspection method using the communication device.
2. Description of the Related Art
In recent years, electric vehicles and hybrid vehicles, each of which is equipped with devices such as a motor and a battery, and runs by driving the motor with electric power stored in the battery, have come to be widespread. An electric vehicle charges a battery by feeding power from an external power feeding device. Also for hybrid vehicles, a plug-in hybrid vehicle which enables its battery to be charged from an external power feeding device has been put in practical use. The external power feeding device corresponds to a power feeding device installed in facilities such as general houses and commercial power feeding stations. In feeding power from the power feeding device to a vehicle, a plug at the tip end of a charge cable connected to the power feeding device becomes connected to a feed port provided at a vehicle as a power receiving connector. Power is then fed from the power feeding device to the vehicle through a feed line enclosed in the charge cable to charge a battery.
It is noted that the charge cable also encloses wiring other than the feed line, e.g., a ground line and a control line. The control line is wiring used to transmit control signals such as a control pilot signal used for feed control of an electric storage device. By transmitting and receiving control signals between a power feeding device and a vehicle through the control line, various states, such as the connection state of a charge cable, the state of a battery as to whether it is chargeable and the state of charging, may be detected so as to perform charge control in accordance with the detected state.
Furthermore, when a vehicle required to be externally supplied with power such as an electric vehicle or a hybrid vehicle is put to practical use, it is necessary to have a communication function for transmitting and receiving information for charge control as well as communication information for managing the amount of charged power, the billing or the like.
Thus, standardization of communication such as power line communication has been in progress, in which communication is performed between a vehicle and a power feeding device by superimposing communication signals using a feed line as a medium. As for a method of transmitting and receiving communication signals, standardization has also been in progress not only for power line communication but also for other types of communication such as in-band communication for transmitting and receiving signals between a vehicle and a power feeding device by superimposing communication signals onto control signals using a control line as a medium (see SURFACE VEHICLE RECOMMENDED PRACTICE, J1772, October 1996 (Revised in January 2010), Society of Automotive Engineers, Inc., for example).
In communication such as power line communication and in-band communication, a superimposition/separation unit using a transformer provided with a primary coil and a secondary coil for wiring such as a feed line, a ground line and a control line. The superimposition/separation unit superimposes and separates communication signals input/output from a communication device connected through a communication line onto/from wiring so as to perform communication between a vehicle and a power feeding device.